gma i2c: Rework GMBUS reset procedure
Once we tried to use the GMBUS controller with an unconnected pair of
I2C pins, it got stuck and a reset via the SOFTWARE_CLEAR_INTERRUPT
bit didn't suffice to recover. Further tests have shown that we are
able to recover, if we switch to a valid pin pair first and issue an
I2C stop cycle before the reset.
Change-Id: If737ffb35afa309de7746f0c16025b9598f69460
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/libgfxinit/+/32730
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/common/hw-gfx-gma-i2c.adb b/common/hw-gfx-gma-i2c.adb
index bc81734..3d41174 100644
--- a/common/hw-gfx-gma-i2c.adb
+++ b/common/hw-gfx-gma-i2c.adb
@@ -122,27 +122,39 @@
----------------------------------------------------------------------------
- procedure GMBUS_Ready (Result : out Boolean)
+ function GMBUS_Ready (GMBUS2 : Word32) return Boolean is
+ ((GMBUS2 and (GMBUS2_HARDWARE_WAIT_PHASE or
+ GMBUS2_SLAVE_STALL_TIMEOUT_ERROR or
+ GMBUS2_GMBUS_INTERRUPT_STATUS or
+ GMBUS2_NAK_INDICATOR or
+ GMBUS2_GMBUS_ACTIVE)) = 0);
+
+ procedure Check_And_Reset (Success : out Boolean)
is
GMBUS2 : Word32;
begin
- Registers.Read (GMBUS_Regs (2), GMBUS2);
- Result := (GMBUS2 and (GMBUS2_HARDWARE_WAIT_PHASE or
- GMBUS2_SLAVE_STALL_TIMEOUT_ERROR or
- GMBUS2_GMBUS_INTERRUPT_STATUS or
- GMBUS2_NAK_INDICATOR)) = 0;
- end GMBUS_Ready;
-
- procedure Reset_GMBUS (Success : out Boolean) is
- begin
pragma Debug (Debug.Put_Line (GNAT.Source_Info.Enclosing_Entity));
- Registers.Write (GMBUS_Regs (1), GMBUS1_SOFTWARE_CLEAR_INTERRUPT);
- Registers.Write (GMBUS_Regs (1), 0);
- Registers.Write (GMBUS_Regs (0), GMBUS0_PIN_PAIR_SELECT_NONE);
+ Registers.Read (GMBUS_Regs (2), GMBUS2);
+ if (GMBUS2 and GMBUS2_GMBUS_ACTIVE) /= 0 then
+ Registers.Write
+ (Register => GMBUS_Regs (1),
+ Value => GMBUS1_SOFTWARE_READY or GMBUS1_BUS_CYCLE_STOP);
+ Registers.Wait_Unset_Mask
+ (Register => GMBUS_Regs (2),
+ Mask => GMBUS2_GMBUS_ACTIVE,
+ TOut_MS => 1);
+ Registers.Read (GMBUS_Regs (2), GMBUS2);
+ end if;
+ Success := GMBUS_Ready (GMBUS2);
- GMBUS_Ready (Success);
- end Reset_GMBUS;
+ if not Success then
+ Registers.Write (GMBUS_Regs (1), GMBUS1_SOFTWARE_CLEAR_INTERRUPT);
+ Registers.Write (GMBUS_Regs (1), 0);
+ Registers.Read (GMBUS_Regs (2), GMBUS2);
+ Success := GMBUS_Ready (GMBUS2);
+ end if;
+ end Check_And_Reset;
procedure Init_GMBUS (Port : PCH_Port; Success : out Boolean) is
begin
@@ -157,23 +169,19 @@
-- TODO: Refactor + check for timeout.
Registers.Wait_Unset_Mask (GMBUS_Regs (2), GMBUS2_INUSE);
- GMBUS_Ready (Success);
- if not Success then
- Reset_GMBUS (Success);
- end if;
+ Registers.Write (GMBUS_Regs (4), 0);
+ Registers.Write (GMBUS_Regs (5), 0);
- if Success then
- Registers.Write
- (Register => GMBUS_Regs (0),
- Value => GMBUS0_GMBUS_RATE_SELECT_100KHZ or
- GMBUS0_PIN_PAIR_SELECT (Port));
- Registers.Write
- (Register => GMBUS_Regs (4),
- Value => 0);
- Registers.Write
- (Register => GMBUS_Regs (5),
- Value => 0);
- end if;
+ -- Resetting the state machine only works if a valid port
+ -- is selected and we don't always know which ports are
+ -- valid. So do the cleanup before we use the GMBUS with
+ -- the current port. If the port is valid, the reset should
+ -- work, if not, it shouldn't matter.
+ Registers.Write
+ (Register => GMBUS_Regs (0),
+ Value => GMBUS0_GMBUS_RATE_SELECT_100KHZ or
+ GMBUS0_PIN_PAIR_SELECT (Port));
+ Check_And_Reset (Success);
end Init_GMBUS;
procedure Release_GMBUS